a) Field of the Invention
The present invention relates to a technique of forming a minute hollow in a semiconductor substrate, particularly in a silicon substrate.
A minute hollow formed in a silicon substrate can be used as a micro machine, a fine pressure gauge, a fine vacuum tube, and the like. A combination of a minute hollow forming technique and a semiconductor process technique of forming an integrated circuit on a silicon substrate allows both an electronic circuit and a minute hollow to be formed on the same substrate, and provides a variety of applications.
b) Description of the Related Art
Conventional-techniques of working a silicon substrate are, for example, anisotropic etching such as reactive ion etching (RIE) which etches a substrate surface only in a vertical direction, and such anisotropic etching as etching a substrate surface by KOH aqueous solution or the like at an etching rate which changes with a Miller index of a crystal plane.